The HIV Center for Clinical and Behavioral Studies is dedicated to multidisciplinary research on the prevention and transmission of HIV and on the improvement of HIV-infected people's lives with an emphasis on sexual risk behavior and the critical role of gender in effective interventions. We are proposing six Cores: (1) the Administrative Core, to provide the leadership to both stimulate and manage innovative research, ensuring the highest scientific standards, ethical integrity, and efficient fiscal operations;(2) the Interdisciplinary Research Methods Core, to provide consultation and oversight for HIV-related sexuality research (including theoretical conceptualization, qualitative and quantitative measurement, and intervention development) and a forum for analysis of theoretical and methodological issues in HIV prevention science;(3) the Statistics. Epidemiology, and Data Management Core, to provide a centralized resource for statistical planning and analysis, for expert consultation on study design and execution, and for data management;(4) the Development Core, to increase the capacity of Center investigators to undertake innovative research consistent with the overall mission of the Center through use of emerging information technologies, pilot study support for new research and training in grant application development, and training support for junior investigators in the academic writing and publishing process;(5) the Ethics and Policy Core, to identify and frame ethical and policy questions in HIV prevention and care that require systematic empirical analysis and to provide education on ethical and policy issues;and (6) the Global Community Core, to identify opportunities for research partnerships in the US and globally that will enhance the generation and adoption into practice of research on HIV/AIDS, interface with major new global public health initiatives, and to develop theoretical models and methodologies to understand and advance the collaborative process and optimize partnerships. Having successfully completed the mandated transition from a P50 to a P30 mechanism in 2002, the HIV Center provides a rich, value-added resource to a large number of investigators, while increasingly attracting and training new investigators and making innovative scientific, programmatic, and policy contributions that respond to the evolving HIV/AIDS epidemic on a national and international level.